In fact, the blowback is so intense, the course now says it might close on September 11 because management is "worried about what people will do/say to our staff."

While some Facebook commenters defended the course and said those offended by the ad were making a mountain of a molehill, most of the response was negative. Here's a sampling (check out Tumbledown's Facebook page here):

As comments like those rolled in, Tumbledown officials attempted to apologize. Suffice it to say their apology wasn't universally accepted:

Tumbledown's latest update, posted last night, indicates the extent to which the ill-advised promotion backfired.

"Please stay tuned to see if we will be open on Weds 9/11," it says. "We are now worried about what people will do/say to our staff & do not want anything to happen or get out of control."

-- Follow Aaron Rupar on Twitter at @atrupar. Got a tip? Drop him a line at arupar@citypages.com.